1. Field of the Invention
The present invention relates to a method and apparatus for measuring the concentration of an objective solvent in a mixed solution. The present invention may be applied for process control in the chemical industry, the food industry and the medical and pharmaceutical industries, environmental measurement, medical diagnosis, etc.
2. Description of the Prior Art
Conventional methods of measuring the concentration of an objective solvent in a mixed solution are classified according to measurement of (1) an absorption spectrum, (2) the absorbency of the solution by coloring the objective solvent with a color coupler, (3) the electrical conductivity of the mixed solution, (4) the index of refraction of the mixed solution, and (5) the specific gravity of the mixed solution.
Methods (1), (3), (4), and (5) are not suitable for continuous measurement. Moreover method (1) needs a large measuring apparatus, method (2) is applicable only to the measurement of the concentration of a colorable objective solvent, and method (3) applies only to the measurement of the concentration of an objective solvent in an electrically conductive mixed solution.